Rock-drill bit



Nov. 22, 1927. t l 1,650,492

A. A. oAToN ROCK DRILL BIT Filed Nov. 11, 1925 rl 4, I

4 FE M Patented Nov. 22, 1927.

i nir e n sr te a ARTHUR ALLAN CGATON, OF SPRINGS, SOUTH AFRICA.

ROCKDRILL BIT.

Application filed November 11, 1926, Serial No. 147,785, and in the Union of South Africa January 5, 1926.

Figs. I, II and III are respectively a side elevation, front elevation and plan of a rock drill tool embodying` the invention.

Fig. IV is a perspective view of the same tool.

Fig. V is a similar vieiv of another form of tool. Figs. VI, VII and VIII shovv a modification of the tool illustrated in Figs.

. I to IV.

The type of tool to which the invention refers comprises a stem 12, at the cutting` end of which is formed a wing (or several wings) terminating in inclined faces 5 which meet to form the transverse cutting edge Il. Each lateral surface l1 of the hevelled end of the Wing is so shaped that the edges 8 formed hy its intersections With the faces lie on a cylinder coaxial with the tool.

According to this invention said surface ll is formed as a portion of a cylinder the axis of which is perpendicular to the axis of the tool. It is desirable that a diameter of such cylinder should coincide with the cutting edge 4; and itis further desirable that the diameter of such cylinder should he equal to the diameter of the tool over the points 10. y

Figs. I to IV shoT the invention carried out in a chisel end forged from the drill stem l2. In these figures 4 is the cutting edge and 8 the reaming edges of the Wing. Fig. V shovvs the more commonly used cruciform tool having tivo such Wings at right angles to one another.

The tools shown in Figs. I to V have complete clearance away from the reaming edges; but it is sometimes desirable, espe` cially when the tool is to he used in hard rock, to employ a modified form which effects a' compromise in the matterof clearance, with the object of maintaining the gauge of the tool for longer periods.

With this ohjectA the drill Wing is firstk forged tothe form previously described, hut-as indicated hy the dotted lines 18 in F ig. V III-to a rather greater diameter than the desired finished diameter. rlfhe tool is thereafter squeezed to final dimensions in a cylindrical die co-axial With the tool and of the desired finished diameter of the tool. lhe eifect is to form, adjacent to the reaming edges 8, cylindrical areas 14 shown in Figs.

VI and VII which may heV regarded as part of the surface of cylinder 2. 'Ihese surfaces take the Wear on the side of the bit and protect the edges 8; and if they are kept small, they do not materiallyldetract from the freedom of the tool to move in the bore 2. A percussive rock drill tool the cutting Y end of Which'is defined by faces sloped to the axis of the tooland intersectingto form a transverse cutting edge, and by lateral surfaces of cylindrical form, having a diameter coincidentvvvith the 'cutting edge and havingl their axial direction perpendicular to the tool axis.

3. "A percussive rock drill tool the cutting end of which is defined hy faces sloped at l5 degrees to the axis of the tool and intersecting to form a transverse cutting edge, and by lateral cylindrical surfaces of the same diameter as the cutting edge having their axis perpendicular to the axis of the' tool and having a diam-eter coincident with the cutting edge. v

4. A. percussive rock drill tool the cutting end of which is defined by faces sloped to the axis of the tool and intersecting to form a transverse cutting edge, and by lateral surfaces of cylindrical formation the axial direction of Which is perpendicular to the tool axis, and also by cylindrical surfaces coaxial ivitli the tool and of the same diameter as the cutting edge and including the lateral edges of the sloped faces.

In testimonv whereof I aiiix my signature.

, ARTHUR yALLAN COATON. 

